Search found 52 matches

by Cynthia Tsang
Sat Mar 17, 2018 9:51 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Solve for Q
Replies: 2
Views: 165

Re: Solve for Q

Q = [concentration of products] / [concentration of reactants]

Because the molarities/partial pressures of all of the components in the Q equation are given, you simply plug and chug. I believe we may have a different test version so I did not get the same answer as you.
by Cynthia Tsang
Sat Mar 17, 2018 9:48 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2 Question 8
Replies: 1
Views: 170

Re: Test 2 Question 8

There are two ways to calculate E(cell) with the E(knot) values of the half reactions. Method 1: 1. Reverse the anode half-reaction. 2. Keep the E(knot) value the same. 3. Use E(cathode) - E(anode) without changing the sign for the anode reaction, but using the reverse reaction. Method 2: 1. Reverse...
by Cynthia Tsang
Sat Mar 17, 2018 9:45 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2 #3
Replies: 2
Views: 191

Re: Test 2 #3

I got something different, but that k value would correspond to a spontaneous reaction.
by Cynthia Tsang
Sat Mar 10, 2018 5:41 pm
Forum: Experimental Details
Topic: Homework Problem 15.3 Part C
Replies: 5
Views: 228

Re: Homework Problem 15.3 Part C

The unique rate is just the basic rate of reaction. When you multiply a coefficient of a reactant by the unique rate, you get the rate of reaction of that compound.
by Cynthia Tsang
Sat Mar 10, 2018 5:39 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: The First Law
Replies: 6
Views: 300

Re: The First Law

The first law and the conservation of energy are the same. The first law just specifies for isolated systems because it is in discussion of thermodynamics.
by Cynthia Tsang
Sat Mar 10, 2018 5:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: The universe as a thermodynamic system [ENDORSED]
Replies: 3
Views: 201

Re: The universe as a thermodynamic system [ENDORSED]

In addition, the universe does not exchange heat or matter with anything beyond it, as there is nothing to do this with. So it is isolated.
by Cynthia Tsang
Wed Feb 28, 2018 12:04 am
Forum: General Rate Laws
Topic: Will we ever deal with third order reactions?
Replies: 2
Views: 68

Re: Will we ever deal with third order reactions?

Lavelle said third and fourth reactions won't be tested on, but we might cover them a little. He has intimated them a bit in our lectures.
by Cynthia Tsang
Wed Feb 28, 2018 12:03 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: What is the order of the reaction? [ENDORSED]
Replies: 4
Views: 122

Re: What is the order of the reaction? [ENDORSED]

If there are multiple reactants, you add up the exponents to find the total order of the reaction.
by Cynthia Tsang
Wed Feb 28, 2018 12:00 am
Forum: General Rate Laws
Topic: Negative in 15.5
Replies: 3
Views: 147

Re: Negative in 15.5

Since the question is asking for the rate at which O2 reacts, the negative is implied with the question.
by Cynthia Tsang
Thu Feb 22, 2018 9:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: The order of cell diagrams
Replies: 1
Views: 75

Re: The order of cell diagrams

Nope, as long as you separate the same phases with commas and the different phases with a single line.
by Cynthia Tsang
Wed Feb 21, 2018 1:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 3
Views: 91

Re: Cell Diagram Order

No, the order doesn't matter.
by Cynthia Tsang
Fri Feb 16, 2018 6:35 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Effect of solids and liquids on K
Replies: 3
Views: 104

Re: Effect of solids and liquids on K

Gases are also included in equilibrium solutions.
by Cynthia Tsang
Fri Feb 16, 2018 6:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Equilibrium
Replies: 4
Views: 78

Re: Equilibrium

I think the current stops because there is no longer a need for transfer of electrons, but I'm not sure.
by Cynthia Tsang
Fri Feb 16, 2018 6:29 pm
Forum: Balancing Redox Reactions
Topic: Basic vs Acidic
Replies: 2
Views: 98

Re: Basic vs Acidic

Then you have to make sure you balance the charges as well with electrons!
by Cynthia Tsang
Sat Feb 10, 2018 8:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: deltaG=0, Phases Coexist ?
Replies: 2
Views: 127

Re: deltaG=0, Phases Coexist ?

Some are liquid particles and loosely bound together and others are gaseous and flowing throughout the mixture.
by Cynthia Tsang
Sat Feb 10, 2018 8:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Table 8.3
Replies: 1
Views: 80

Re: Table 8.3

Since the textbook said to specifically use the table, I would use the value from there. On the test, you would use the 40 kJ value and that would be fine.
by Cynthia Tsang
Sat Feb 03, 2018 11:45 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible and irreversible with entropy
Replies: 2
Views: 89

Re: reversible and irreversible with entropy

No you won't ever use q(irrev) to calculate the deltaS, but you can use the fact that entropy is a state function to find the amount of energy needed for an irreversible reaction.
by Cynthia Tsang
Sat Feb 03, 2018 11:44 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How to tell what happens to entropy by seeing a reaction?
Replies: 6
Views: 186

Re: How to tell what happens to entropy by seeing a reaction?

Like mentioned above, since the entropy of the products is higher, the total entropy would be a positive value.
by Cynthia Tsang
Sat Feb 03, 2018 11:40 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: deltaG at equilibrium
Replies: 5
Views: 111

Re: deltaG at equilibrium

deltaG = 0 at equilibrium, so that might be an indicator, but I'm not sure if that would be given.
by Cynthia Tsang
Thu Jan 25, 2018 6:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: exothermic vs endothermic [ENDORSED]
Replies: 7
Views: 262

Re: exothermic vs endothermic [ENDORSED]

The calorimeter can also be apart of the surroundings, as some calorimeters absorb some of the heat released in the reaction. In general though, the water is the surrounding and whatever you're adding is the system.
by Cynthia Tsang
Thu Jan 25, 2018 6:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.1 Entropy Higher or Lower at Higher Temperatures
Replies: 2
Views: 71

Re: 9.1 Entropy Higher or Lower at Higher Temperatures

There is actually an equation stating deltaS = -(deltaH)/T. Because of this, we can infer that deltaS is smaller in this situation.
by Cynthia Tsang
Mon Jan 22, 2018 12:25 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Week 3 Homework [ENDORSED]
Replies: 1
Views: 102

Week 3 Homework [ENDORSED]

What chapter of homework do we need to do for this week? My TA said we should submit chapter 9 homework, but I have discussion Wednesday morning and we have barely touched on Chapter 9 topics.
by Cynthia Tsang
Fri Jan 19, 2018 5:32 pm
Forum: Calculating Work of Expansion
Topic: work done on and by the system
Replies: 12
Views: 435

Re: work done on and by the system

Work is negative when the system does work. Work is positive when work is done on the system.
by Cynthia Tsang
Fri Jan 19, 2018 5:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.99
Replies: 2
Views: 93

Re: Problem 8.99

For the second question, the 800g comes from the 800 mL of water. Recall that water has a density of 1g/mL so this is used to change the volume to mass. Densities for other substances will be provided, but that's a good one to remember.
by Cynthia Tsang
Fri Jan 19, 2018 5:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.99
Replies: 2
Views: 93

Re: Problem 8.99

For the first question, standard energy of formations are 0 when a compound is in its most stable, standard state. The definition of standard enthalpy of formation is the amount of energy required to create a 1 mole of a substance from its original standard state. Examples include O2, H2, I2. Br2, h...
by Cynthia Tsang
Fri Jan 19, 2018 5:06 pm
Forum: Phase Changes & Related Calculations
Topic: 8.23
Replies: 5
Views: 299

Re: 8.23

q = C (delta T) is also an equation that works, although I'm not sure when each is applied.
by Cynthia Tsang
Fri Jan 12, 2018 4:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework grading
Replies: 6
Views: 244

Re: Homework grading

In general though, I think they're graded for correctness.
by Cynthia Tsang
Fri Jan 12, 2018 4:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: tables in chapter 8
Replies: 5
Views: 187

Re: tables in chapter 8

He said in class today that all values will be given!
by Cynthia Tsang
Fri Jan 12, 2018 4:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy formula from day 1
Replies: 2
Views: 122

Re: Enthalpy formula from day 1

Because the pressure is not changing, none of the heat being released is going into the surroundings. This would make the change a closed system and all of the heat released in a reaction would equal the enthalpy of the reaction.
by Cynthia Tsang
Sun Dec 10, 2017 4:42 pm
Forum: Amphoteric Compounds
Topic: amphiprotic vs. amphoteric [ENDORSED]
Replies: 2
Views: 409

Re: amphiprotic vs. amphoteric [ENDORSED]

They are similar but amphiprotic is more specific. Amphiprotic is when something can donate or receive a proton. Amphoteric is when something can act as an acid or a base.
by Cynthia Tsang
Wed Dec 06, 2017 3:20 pm
Forum: Dipole Moments
Topic: Dipole Moments and Polarity
Replies: 9
Views: 307

Re: Dipole Moments and Polarity

In trigonal bi-pyramidal, there is no dipole moment because the five atoms around the central atom are evenly spread and symmetrical. For square pyramidal though, where there is a lone pair and 5 bonds to other atoms, this would form a dipole moment.
by Cynthia Tsang
Mon Nov 27, 2017 9:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Assuming x is negligible
Replies: 3
Views: 149

Assuming x is negligible

When can you assume that, in your ICE table, x is negligible and can be removed from your equilibrium constant equation?
by Cynthia Tsang
Mon Nov 27, 2017 9:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gas Equilibrium Constant
Replies: 1
Views: 87

Gas Equilibrium Constant

If given the reaction 2 NO2(g) + F2(g) <-> 2 FNO2(g) are the following equilibrium constants the same? If not, what are the differences and what units or information do you input into each one? K = \frac{[FNO_{2}]^{2}}{[F^{2}][NO_{2}]^{2}} vs. K = \frac{[P_{FNO_{2})}]^2}{[P_{F_{2}}][P_{NO_{2}}]^...
by Cynthia Tsang
Thu Nov 23, 2017 12:14 pm
Forum: Hybridization
Topic: Pi Bonds vs. Sigma Bonds
Replies: 7
Views: 263

Re: Pi Bonds vs. Sigma Bonds

Sigma bonds are always the first bonds that form. Pi bonds are all the bonds after that. So the second and triple bond are pi bonds and the first bond is still a sigma bond.
by Cynthia Tsang
Thu Nov 23, 2017 12:11 pm
Forum: Naming
Topic: Naming the metal
Replies: 4
Views: 139

Re: Naming the metal

Yup! -ate is only used when the transition metal forms an anion.
by Cynthia Tsang
Sat Nov 18, 2017 9:04 pm
Forum: Hybridization
Topic: Why is (CH3)2Be is sp? [ENDORSED]
Replies: 7
Views: 3078

Re: Why is (CH3)2Be is sp? [ENDORSED]

The central atom is always the one with the lowest electronegativity. Be is lower than C so it is in between the two carbons
by Cynthia Tsang
Sat Nov 18, 2017 9:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 3
Views: 144

Re: Bond angles

Lone pairs provide more repulsion than other atoms with electrons attached. Therefore the angles between the lone pairs and the atoms will be bigger than expected for the shape, and the angles between the atoms will be smaller because the lone pair pushes them closer together.
by Cynthia Tsang
Fri Nov 10, 2017 9:52 am
Forum: Ionic & Covalent Bonds
Topic: Midterm
Replies: 6
Views: 345

Re: Midterm

I think it was SO2. KCl was ionic. SO2 was polar and N2 was nonpolar.
by Cynthia Tsang
Fri Nov 10, 2017 9:52 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Practice Midterm Extra Practice #5
Replies: 1
Views: 124

Re: Practice Midterm Extra Practice #5

So you find that the indeterminacy of the position of the gutter ball is an extremely small number -- about 2.42 x 10^-34 m. This is less than a single millimeter, so you cannot blame the Heisenberg Principle for a gutter ball because the principle would only shift your bowling ball an extremely sma...
by Cynthia Tsang
Thu Nov 02, 2017 2:44 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 2
Views: 149

Re: Lone Pairs

So when you draw molecules, such as CO2, there are a total of 16 electrons present. Carbon has 4 valence electrons and oxygen has 6. So you draw the structure and find that Carbon is in the center and has the oxygens on the side. They are connected with double bonds. Carbon has used all of its valen...
by Cynthia Tsang
Thu Nov 02, 2017 2:39 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity and Ionization Energy
Replies: 1
Views: 132

Re: Electron Affinity and Ionization Energy

Well electron affinity and ionization are fundamentally different things. Electron affinity is the change in energy of an atom for adding an electron. When observed in reactions, it's shown that adding an electron is actually exothermic, meaning it releases energy, instead of needing energy to add e...
by Cynthia Tsang
Tue Oct 24, 2017 6:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Weekly online discussion points
Replies: 3
Views: 221

Re: Weekly online discussion points

I'm pretty sure he'll enter it all in at once or else it would be such a hassle. Someone should ask him in class or ask their TA though.
by Cynthia Tsang
Tue Oct 24, 2017 6:31 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Question on the difference between quantum numbers l and ml.
Replies: 3
Views: 204

Re: Question on the difference between quantum numbers l and ml.

So l is the momentum of the electron rotating around the nucleus. Ml on the other hand, is the angle at which the electron is rotating around the nucleus. If you look at orbitals and their different shapes, you'll see that each ml has a different orbital shape and this ml number determines exactly w...
by Cynthia Tsang
Sat Oct 21, 2017 5:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hund's Rule [ENDORSED]
Replies: 6
Views: 319

Re: Hund's Rule [ENDORSED]

Hund's Rule basically states that every orbital shell is to be occupied by an electron before any orbital is occupied with two electrons. Usually this means that one spin direction is occupied for all the orbital shells before the opposite spin direction occupies the orbital to fill the shells.
by Cynthia Tsang
Sat Oct 21, 2017 5:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation! [ENDORSED]
Replies: 8
Views: 513

Re: Rydberg Equation! [ENDORSED]

Frequency can't be negative, but I've noticed that when you switch the two original n-values, one will result in a negative frequency and one will result in the same positive frequency. So whatever value you get, just take the positive form of it and continue.
by Cynthia Tsang
Fri Oct 13, 2017 3:25 pm
Forum: Empirical & Molecular Formulas
Topic: Test 1 Compound X [ENDORSED]
Replies: 5
Views: 323

Re: Test 1 Compound X [ENDORSED]

So you are given the mass of CO2 and H2O. You convert these both to moles. We can start with CO2. 7.48 grams of CO2 is 0.16996 moles of CO2. You multiple this value by (1 mol of C/1 mol of CO2) to isolate the moles of C. This will give you 0.16996 moles of C. You do the same for oxygen, multiplying ...
by Cynthia Tsang
Fri Oct 13, 2017 3:12 pm
Forum: Properties of Electrons
Topic: 1/2mv^2
Replies: 2
Views: 168

Re: 1/2mv^2

This equation is for kinetic energy. The total energy of a photon is composed of two energies: threshold and kinetic. The threshold energy is the energy needed to free or move an electron. The kinetic energy is the remaining energy, assuming the energy of the photon is greater than the threshold ene...
by Cynthia Tsang
Tue Oct 03, 2017 11:32 pm
Forum: Molarity, Solutions, Dilutions
Topic: Atoms
Replies: 3
Views: 343

Re: Atoms

If they give you the mass of the compound, you convert it to moles, with the molar mass, and then multiple it by Avogadro's number! That's the amount of atoms that are in each mole of anything.
by Cynthia Tsang
Tue Oct 03, 2017 11:30 pm
Forum: SI Units, Unit Conversions
Topic: Appendix 1D & 1E
Replies: 3
Views: 212

Re: Appendix 1D & 1E

I think all of the appendixes are just for reference in the future. It doesn't necessarily mean we'll be tested on them!

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